Tetracarbonyl(trifluoromethyl)cobalt(I) [Co(CO)4(CF3)] as a Precursor to New Cobalt Trifluoromethyl and Difluorocarbene Complexes

An improved synthesis of the known trifluoromethyl cobalt compound Co­(CO)4(CF3) (1), which gives significantly higher yields than previously reported methods, allows for an investigation of its carbonyl substitution chemistry. Treatment of 1 with P-donor ligands of varying denticity under thermal conditions afforded Co­[P­(O-o-tolyl)3]­(CO)3(CF3) (2), Co­(DPPE)­(CO)2(CF3) (3), and Co­(P3)­(CO)­(CF3) (4) in high isolated yields [DPPE = Ph2PCH2CH2PPh2; P3 = PhP­(CH2CH2PPh2)2]. The new cobalt N-heterocyclic carbene complex Co­(SIPr)­(CO)3(CF3) (5) [SIPr = 1,3-bis­(2,6-diisopropylphenyl)­imidazolidin-2-ylidene)] was obtained by phosphine substitution from Co­(PPh3)­(CO)3(CF3), a known compound efficiently prepared from 1. Additionally, we report the synthesis of two rare cobalt difluorocarbene complexes ([Co] = CF2) produced by fluoride abstraction from 3 or 4. These results are relevant to our efforts to assess the reactivity of first-row metal perfluoroalkyl and fluorocarbene complexes.